In the past much effort has been put in approaches for resource bundling which can be roughly grouped into: session/application-, transport-, network- and link-layer approaches. In the following the most important examples for each of these groups will be briefly discussed.
The HTTP range request is a session/application-layer feature which can also be used to perform resource bundling. This feature divides the content to download into slices which are then downloaded in separate TCP sessions over different interfaces. This feature is implemented within the Samsung Galaxy S5 and called “Network Booster” (S. E. Corporation, “Network booster—for enhanced data performance,” Techpaper).
The most prominent example of a transport-layer solution is Multipath TCP (MPTCP) specified by the Internet Engineering Task Force (IETF) in Request for Comment (RFC) 6824 (A. Ford, C. Raiciu, M. Handley, and O. Bonaventure, “Tcp extensions for multipath operation with multiple addresses,” RFC, no. 6824, January 2013). MPTCP can be seen as an extension of TCP which allows the simultaneous usage of multiple paths between peers transparent for the application. MPTCP is already used in commercial products like the iPhone. The Siri service for instance uses MPTCP to increase reliability. In case the iPhone has a cellular and a Wi-Fi connection Siri initiates two sessions one over Wi-Fi and one over the cellular network. If one of the connections becomes unavailable or unreliable, the backup connection is immediately available.
Another transport-layer example is Stream Control Transmission Protocol (SCTP) (R. Stewart et al., “Stream Control Transmission Protocol,” RFC 2960 (Proposed Standard), Internet Engineering Task Force, October 2000, obsoleted by RFC 4960, updated by RFC 3309). One of the advantages of SCTP is its multi-homing feature which in principle also enables the bundling of links.
In principle it can be stated that the session/application layer approaches as well as the transport layer approaches are suited for end-to-end (E2E) scenarios as the bundling is performed by the end-devices without any special involvement of the network. The drawback of E2E approaches is the effort of introducing the technology as it must be supported by the user devices as well as the Internet servers.
Network-layer approaches are the preferred solution for network operators as they can easily be implemented without the need to change the end-devices. Instead proxy servers are used, which are under the control of the operator and which perform the bundling transparent to the end devices.
Link-layer bundling refers to the bundling of multiple channels of equal technology. Examples are the bundling of Ethernet links defined in IEEE 802.3ad (WO 2009/019258 A1) and the bundling of Wi-Fi channels for instance implemented in the Atheros SuperG mode. The SmartAP solution proposed in (E. G. Llairo and D. Giustiniano, “Smartap: Practical wlan backhaul aggregation.” in Wireless Days. IEEE, 2013, pp. 1-7) deals with the aggregation of Wireless Local Area Network (WLAN) backhaul using single-radio multi-channel visualisation. This allows connections with multiple neighbouring Access Points (APs) even if different channels are used. D. Giustiniano, E. Goma, A. Lopez Toledo, I. Dangerfield, J. Morillo, and P. Rodriguez, “Fair wlan backhaul aggregation,” in Proceedings of the Sixteenth Annual International Conference on Mobile Computing and Networking, ser. MobiCom '10. New York, N.Y., USA: ACM, 2010, pp. 269-280 investigates fairness in the described system.